Manufacture of monomethyl-paraaminophenol and its sulphate



Patented Mar. 5, 1935 MANUFACTURE OF MONOMETHYL-PARA AMINOPHENOL AND'ITS SULPHATE i Charles H. W. Whitaker, Marietta, hio,- assignor of seventy-five one-hundredths to Industrial Dyestufi Company, East'Providence, R.'jI.,.a' corporation of Rhode Island No Drawing.

Application September 18,1934,- Serial No. 744,609 g '17 Claims. (01., tom-12s) The instant application is a continuation in part of my earlier application, Serial No.1680,50'7, filed July 14,1933. I

, This invention relates to improvements i'nthe manufacture of N-methyl-para-aminophenol sulphate, and more particularly to improvements in the process of converting para-hydroxy-phenyl- .glycine into N-monomethyl-para-aminophenol, which, in turn, is converted into the sulphate.

- It is well known that by heating para-hydroxyphenylglycine in the presence of a large excess of phenol to about 170 C., decomposition of the glycine occurs with the formation of N-methylpara-aminophenol. It has recently been proposed to employ an' excess of cresylic acid or other protective media, such as xylenols, thymol, carvae crol, and benzaldehyde, in place of phenol, at temperatures ranging from 165 C. to 185C. The proportions of these mediaemployed are generally from ten to'twelve times the weight of the glycine.

It has been extremely difiicult to find media which are not required in such large amounts in order to complete the decomposition of the glycine in a reasonabletime and which do not resinify when heated for long periods in contact with methylated aminophenol, especially when used in large scale-production inthe factory. It has also been difficult to prevent decomposition of 3p; N-methyl-para-aminophenol formed during the heat treatment. Decomposition of the N'-methylpara-aminophenol and resinificati'on' seriously affeet the yield of the finished N-methyl-paraaminophenol sulphate, as well as the recovery of the media. V An object of the present invention is, therefore, to provide a process in which the aforesaid 'difliculties, particularly that of preventing resini- 'fication and that of preventing decomposition of the end'product, are overcome. i I

A further object is to provide a highly eflicient process in'which parahydroxyphenylglycine is decomposed under controlled conditions in a fluid medium of such a nature as will cause a rupture of the glycine grouping at a relatively'low temperature and bring about the completion of the reaction in a relatively short time;

f Another object is to providea relatively inexpensive process by which to carry on the above reaction, and which process permits of'practically complete recovery of the final product and of the mediain which the reaction is carried on.

' The media which are employed in the present "process and havebeen found to be most successful are'the products of the hydrogenation of phenols.

about centigrade. maintained at this point and the :whole'stirred Esters of the alcohols formed. by hydrogenation I of phenols may also be employed.

Of the hydrogenation productions .of' the Va.- rious phenols, I have found that the mostv efiicient is the ketonicderivative formed byv the :35 hydrogenation of. a mixture of the three isomeric 'cresols, commonly referred'toas methyl cyclohexanone. It has the empirical formula C7H12O. The technical'form of this product, usuallly. containing about ten percent of the corresponding alcohol, methyl cyclohexanol, and having alboiling point which varies'between about':160?- and C., is well suited forthis purpose. '6 The following examples serve to illustrate the presentinvention:

l Example 1.-'Into a suitable apparatus charge 350 pounds of technical methyl cyclohexanone s PATENT mice;

and add '70 pounds of dry, powdered para -hydroxyphenylglycine'. The mass is now stirred and heated to attain a'temperature of about 140. :to The temperatur'elis now for" about ninety minutes, until inspection of. a

sample shows that a complete solution has been obtained, following. which it can be concluded that decomposition is at an end. I The mass inthe" 7 apparatus is now cooled externally to Tabout'20" V centigrade, whereupon it-is diluted by the=addi'- tion of about 250 poundsof ethyl alcohol and. the

whole 'well mixed. "The dilutedma'ss isfnow treated with thestoichiometric amount oisconicentrated sulphuric acid, taking care that the temperature of the mixture does not exceed about '30" centigrade. As soon as thesulphuric acid'has been added,'the sulphate of N-monomethyl-paraaminophenol separates :from the. solution and after stirring the mass for a few hours it is filtered off and washed with ethyl alcohol until the mother liquor hasbeenremoved. The residue'is' now dried and may be recrystallized, if desired. The N- -monomethyl-para-aminophenol sulphate'z-is ob- I named in excellent yield and highipurity. By the distillation of the filtrate, the alcohol: and methyl cyclohexan'one are recovered with but small losses, following which they are used in a subsequent batch.- T J I 7 Eater/mole 2.--Into" an apparatus similar to that used in Example 1, charge350 pounds of methyl cyclohexanone of technical grade and'heat' the fluid to a temperature of about 140 to about .145 centigrade. At this point, the heating isI'so'regulated as to'keep the temperature aboutcoristant at'the temperature stated. During a period :of about onehour, charge '70 pounds'of"dry, .pow-

dered' para-hydroxy-phenylglycine,z.theiladditio'n l product in the apparatus can now be worked 'up according to the procedure used in-rt-he above Example 1, or as follows: Add about'700 pounds of water to the mass, stir thoroughly and add the necessary amount ofusulphu'ric acidflto'neutralize the N-methyl-para aminophenolbase and form its sulphate. The whole is now heated to about 80 centigrade, and is then run into a separatory vessel whereby the-aqueous layer; consisting of a solution of N-monomethykparaaminophenol sulphate in water, can beseparated from the residual methyl cyclohexanone. Fol- .lowing thisi the methyl cyclohexanone: can be once more extracted with water" .and acid and, finally; the two extractions are united and evaporatedLdownto dryness, preferably ina. vacuum, cto. avoid' oxidation by air as much-as possible. Therdry productthus obtained is: now, preferably, groundto apowder, mixed with-three or four .times its weight of .alcohol, heated to a"boil, a1- IOWEd tOIOOOLdOWII, filtered off and dried. It is now-obtained in a state of :high purity, butane-y be recrystallized from water, if desired.

:;Although,:in' the above examples, use ismade of technical-methyl cyclohexanone, the reaction rcanr-becarried outwith success by thexuseof the ketonic product formed by the. hydrogenation of either ortho,-'-.meta, or para cresoL although in :thesexcases 'thecost of operation is increased materially. .Furthermore,- I amnot restricted :solely :to the employment of. the hydrogenation products of cresols, since I have found that prodnets :of the hydrogenationof phenols, in general, giveresults superior to those obtained by the use ofnthe: phenols ifrom which :the hydrogenation products are :derived. ,1 have also found that .esters of the alcohols formed by hydrogenating aph'enols 'can 'be usedsuccessfully;

' i The following: examples .will serve to illustrate- 'the utilization of the esters 'of:the alcoholsformed .by' hydrogenating phenolic bodies .Erample' 3.-'15z*par.ts "(by weight) of parahydroxy-aphenylglycine are "mixed with 225 parts (by-weight) of the'acetic ester'of cyclohexanole (cyclohexanole acetate) and the mixture stirred andlheated' .to 170 centigrade. The whole is stirred at 170'to 180 centigrade in-a'closedvessel, fitted with'a descending condenser, which '-:lattercondenses any cyclohexanone acetate which: is entrainedrby the gas evolution. From .itlme 'to .time'the gaszescaping :through the condenser istested for presence 'of carbon dioxide, and' when'it is found that no more carbon-dioxide? is=tbeing liberated the heating is interrrupted andthe reaction vessel is externally cooled to room-temperature. The contentsiof the -vessel are :treated with about IOO-partsof ethyl alcohol, and the whole filtered to remove any .dirt or tarry matter. The filtrateis'nowtreated .-with concentrated sulphuric acid at about room :.temperature=until a test :shows'that the further "addition of acid does notcause any further pre- 'cipitation. .At thispoint; the sulphate of mono- :methyl-paraeaminophenol is out of solution. in a microcrystalline form. The precipitate is then -fllteredofi and-washed with ethyl alcohol until sfreeiromrmotherrliquor, followingwhich it. may

"of' ortho, meta and para cresols) in a closed vessel; fitted .with= a-:descending condenser, as was'described :in Example 1. The mixture is agitated and the temperature maintained at about 180 .centigrade until a test shows that ..no. more carbon dioxide is evolved. The further working. is then carried out precisely as given in Example 3.

,E-mample 5-.-15 parts (by weight) of parahydroxy-phenylglycine is mixed with 225 parts of methyl cyclohexanole benzoate, and the mass placed in a reaction vessel of the type referred to .in 'Exa'mple 3. The whole ismthen heated at aboutl'85 centigradeuntilno further evolution of carbon dioxide is apparent, following which the further working is exactly as already given in iExample 3.

.The-r'detailed examples given above indicate that thexproportionof solvent medium, men- .tioned specifically as methyl cyclohexanone, is 'fivetimesthe weight of the glycine. It is to be understood-however, that a considerable variazticnpis permissible without departing from the spirit. of the invention. If the medium'is used to the extent of twioethe weight of the glycine, a longer-time and a'higher .temperatureis required'to complete the reaction than if :the'medium is used to the extent of, for instance, twenty timesthe weight of theglycine.

1 It'has further-been found in the process of the present invention that the reaction. proceeds advantageously when the parahydroxyphenylglycine is addedto a mixture of a phenol or phenols and thehydrogenation product or productsaofa phenol or phenols. .In this case, the

advantagethat. such a procedure has over a procedure which phenol or phenols are used alone, is substantially in direct proportion'to the concentration of the hydrogenated product insthe medium. ,'-I-he untreated phenol merely dilutes the beneficial effects of the hydrogenated phenol.

What Iclaim is:

1. A process of -manufacturing monomethylpara-aminophenol, which process comprises decomposing parahydroxyphenylglycine to mono- 'methyl-para-aminophenol in a medium containing essentially a hydrogenated phenol product.

.2. Aprocess of manufacturing monomethylpara-aminophenol, which process comprises decomposing para-hydroxyphenlyglycine to monomethylepara-aminophenol in a medium containing essentially an-ester of alcohol formed by the hydrogenation of a phenol.

3. A-process of manufacturing monomethylpara-aminophenol, which process comprises decomposing-para-hydroxyphenlyglycine to mono- .methyl-para-aminophenol in a medium containingessentially acetic ester of cyclohexanole (cyclohexanole acetate).

-4. In-the process set forth in-claim 3, the steps consisting in mixing .15 parts, by weight, of para-hydroxyphenylglycine with 225 parts, by weight, of the acetic ester of cyclohexanole (cyclohexanole acetate), stirring the mixture and heating it to from 170 to 180 centigradein a closed lvessel, interrupting heating of the mixturewhenv liberation of carbon dioxide has ceased and cooling it to room temperature, treating the cooled mixture with parts of ethyl alcohol and. filtering to remove dirt or tarry. matter, treating the filtrate with concentrated sulphuric acid to produce the sulphate of monomethylpara-aminophenol, and then filtering ofl and Washing the precipitate with ethyl alcohol until free from mother liquor.

5. A process of manufacturing monomethylpara-aminophenol, which process comprises decomposing para-hydroxyphenylglycine to monomethyl-para-aminophenol in a medium containing essentially methyl cyclohexanole acetate.

6. In the process set forth in claim 5, the steps consisting in mixing 15 parts, by weight, of parahydroxyphenylglycine with 225 parts of methyl cyclohexanole acetate (the acetic acid ester of the alcohol formed by the hydrogenation of a mixture of ortho, meta and para cresols), agitating the mixture while maintaining it to a temperature of about 180 centigrade until liberation of carbon dioxide has ceased, then cooling it to room temperature, treating the cooled mixture with 100 parts of ethyl alcohol and filtering to remove dirt or tarry matter, treating the filtrate with concentrated sulphuric acid, and then filtering off and washing the precipitate with ethyl alcohol until free from mother liquor.

'7. A process of manufacturing monomethylpara-aminophenol, which process comprises decomposing para-hydroxyphenylglycine to monomethyl-para-aminophenol in a medium containing essentially methyl cyclohexanole benzoate.

8. In the process set forth in claim 7, the steps consisting in mixing 15 parts, by weight, of parahydroxyphenylglycine with 225 parts of methyl cyclohexanole benzoate, agitating the mixture while maintaining it to a temperature of about 185 centigrade until liberation of carbon dioxide has ceased, then cooling it to room temperature, treating the cooled mixture with 100 parts of ethyl alcohol and filtering to remove dirt and tarry matter, treating the filtrate with concentrated sulphuric acid, and then filtering oii and washing the precipitate with ethyl alcohol until free from mother liquor.

9. A process of manufacturing monomethylpara-aminophenol, which prmess comprises decomposing para-hydroxyphenylglycine to monomethyl-para-aminophenol in a medium containing essentially methyl cyclohexanone.

10. A process of manufacturing monomethylpara-aminophenol, which process comprises decomposing para-hydroxyphenylglycine to monoproduct at a temperature of about to about a centigrade.

13. A process of manufacturing monomethylpara-aminophenol, which process comprises heating para-hydroxyphenylglycine in methyl cyclohexanone at a temperature of about 140 to about 145 centigrade.

14. A process of manufacturing monomethylpara-aminophenol, which process comprises decomposing para-hydroxyphenylglycine to monomethyl-para-aminophenol by means of heat in a protecting medium comprising essentially methyl cyclohexanone.

15. A process of manufacturing monomethylpara-aminophenol, which process comprises heating a mixture of para-hydroxyphenylglycine and methyl cyclohexanone, in the proportion of about one part by weight of para-hydroxyphenylglycine to aboutfive parts by weight of methyl cyclohexanone, to a temperature sufiiciently high to cause decomposition of the para-hydroxyphenylglycine without causing decomposition of the methyl cyclohexanone.

16. A process of the character described, comprising decomposing .para-hydroxyphenylglycine to monomethyl-para-aminophenol in the presence of methyl cyclohexanone, and stirring the reaction mixture with a solution containing an amount of sulphuric acid sufficient to convert the monomethyhpara-aminophenol base into monomethyl-para-aminophenol sulphate.

17. A processof the character described, comprising decomposing para-hydroxyphenylglycine to monomethyl-para-aminophenol in the presence of a hydrogenated phenol product, diluting the resulting mass with alcohol, and. adding suflicient sulphuric acid to convert the monomethylpara-aminophenol base into monomethyl-paraaminophenol sulphate.

CHARLES H. W. WHITAKER. 

